If a patient is unable to tolerate one CDK 4/6 inhibitor, do you switch to a different one?

There are currently no data about switching from one CDK 4/6 inhibitor to another. The current recommendations for palbociclib with grade 3 neutropenia and infection are to hold palbociclib until recovery to grade 2 or less and then dose reduce. It sounds as though this patient has required multiple dose reductions and may be at the lowest dose of 75 mg/day. In PALOMA-2, grade 3/4 neutropenia occurred in 66.4% of patients who received palbociclib plus an aromatase inhibitor, with febrile neutropenia in 1.8% (Finn NEJM). In MONARCH 3, the grade 3/4 neutropenia rate was 21.2% with abemaciclib plus an aromatase inhibitor, with 1 patient experiencing febrile neutropenia (0.3%) (Goetz JCO). Thus, though there is an absence of data, it is reasona...

I agree. I have had success switching from palbociclib to abemaciclib for patients with neutropenia, and from one CDK4/6 inhibitor to another for a patient with cutaneous toxicity.

Yes